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ESA???s Mercury mapper feels the heat

BepiColombo’s Mercury Magnetospheric Orbiter in the Large Space Simulator

BepiColombo's Mercury Magnetospheric Orbiter in the Large Space Simulator

ESA –?? Key components of the ESA-led Mercury mapper BepiColombo have been tested in a specially upgraded European space simulator. ESA???s Large Space Simulator is now the most powerful in the world and the only facility capable of reproducing Mercury???s hellish environment for a full-scale spacecraft.

The Mercury Magnetospheric Orbiter (MMO) has survived a simulated voyage to the innermost planet. The octagonal spacecraft, which is Japan???s contribution to BepiColombo, and its ESA sunshield withstood temperatures higher than 350 ??C.

This is a taste of things to come for the spacecraft. BepiColombo will encounter fully ten times the radiation power received by a satellite in orbit around Earth and, to simulate this, the Large Space Simulator (LSS) at ESA???s ESTEC centre in the Netherlands had to be specially adapted.

Engineers talk about the power of the Sun in units called the solar constant. This is how much energy is received every second through a square metre of space at the distance of Earth???s orbit.

???Previously, the LSS was capable of simulating a solar constant or two. Now it has been upgraded to produce ten solar constants,??? says Jan van Casteren, ESA BepiColombo project manager.

The improvements have been achieved in two ways: the lamps from the simulators are being used at their maximum power and the mirrors that focus the beam have been adjusted.

Instead of producing a parallel beam of light 6 m across, they now concentrate the light into a cone just 2.7 m in diameter when it reaches the spacecraft. This creates a beam so fierce that a new shroud with a larger cooling capacity had to be installed to ???catch??? the light that missed the spacecraft and prevent the chamber walls from heating up.

BepiColombo consists of separate modules. The MMO will investigate the magnetic environment of Mercury. It is kept cool during its six-year cruise to Mercury by the sunshield. These are the two modules that have now completed their thermal tests.

???The sunshield test was successful. Its function to protect the MMO spacecraft during the cruise phase was demonstrated,??? says Jan.

Once at Mercury, most of the Sun???s fearsome heat will be prevented from entering BepiColombo by special thermal blankets. They consist of multiple layers including a white ceramic outer layer and several metallic layers to reflect as much heat as possible back into space.

???The tests allowed us to measure the thermal blanket???s performance. The results allow us to prepare some adjustments for the tests of the Mercury Planetary Orbiter next year,??? says Jan.

In addition to enduring temperatures of 350 ??C, ESA???s Mercury Planetary Orbiter (MPO) will go where no spacecraft has gone before: down into a low elliptical orbit around Mercury, of between just 400 km and 1500 km above the planet???s scorching surface.

At that proximity, Mercury is worse than a hot plate on a cooker, releasing floods of infrared radiation into space. So, the MPO will have to deal with this as well as the solar heat. The MPO begins its tests in the LSS in the summer.

What???s on board?

Mercury Planetary Orbiter (ESA)
MPO will carry a highly sophisticated suite of eleven scientific instruments, ten of which will be provided by Principal Investigators through national funding by ESA Member States and one from Russia:

BepiColombo Laser Altimeter (BELA)
BELA will characterise the topography and surface morphology of Mercury. It will also provide a digital terrain model that, compared with the data from the MORE instrument, will allow to obtain information about the internal structure, the geology, the tectonics and the age of the planet???s surface. Co-Principal Investigators: N. Thomas, University of Bern, Switzerland, and T. Spohn, DLR, Germany.

Italian Spring Accelerometer (ISA)
The objectives of the ISA accelerometer are strongly connected with those of the MORE experiment. Together the experiments can give information on Mercury???s interior structure as well as test Einstein???s theory of the General Relativity. Principal Investigator: V. Iafolla, CNR-IFSI, Italy.

Mercury Magnetometer (MERMAG)
MERMAG will provide measurements that will lead to the detailed description of Mercury???s planetary magnetic field and its source, to better understand the origin, evolution and current state of the planetary interior, as well as the interaction between Mercury???s magnetosphere with the planet???s itself and with the solar wind. Principal Investigator: K.H. Glassmeier, Technical University of Braunschweig, Germany.

Mercury Thermal Infrared Spectrometer (MERTIS)
MERTIS will provide detailed information about the mineralogical composition of Mercury???s surface layer with a high spectral resolution, crucial for selecting the valid model for origin and evolution of the planet. Principal Investigator: H. Hiesinger, University of M??nster, Germany.

Mercury Gamma ray and Neutron Spectrometer (MGNS)
MGNS will determine the elemental compositions of the surface and subsurface of Mercury, and will determine the regional distribution of volatile depositions on the polar areas which are permanently shadowed from the Sun. Principal Investigator: I. Mitrofanov, Institute for Space Research, Russia.

Mercury Imaging X-ray Spectrometer (MIXS)
MIXS will use the ???X-ray fluorescence??? analysis method to produce a global map of the surface atomic composition at high spatial resolution. This technique has been also used by the D-CIXS instrument on ESA???s SMART-1 mission to the Moon. Principal Investigator: G. Fraser, University of Leicester, UK.

Mercury Orbiter Radio science Experiment (MORE)
MORE will help to determine the gravity field of Mercury as well as the size and physical state of its core. It will provide crucial experimental constraints to models of the planet???s internal structure and test theories of gravity with unprecedented accuracy. Principal Investigator: L. Iess, University of Rome ???La Sapienza???, Italy.

Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS)
The PHEBUS spectrometer is devoted to the characterisation of Mercury???s exosphere composition and dynamics. It will also search for surface ice layers in permanently shadowed regions of high-latitude craters. Principal Investigator: E. Chassefi??re, Universit?? P&M Curie, France.

Solar Intensity X-ray Spectrometer (SIXS)
SIXS will perform measurements of X-rays and particles of solar origin at high time resolution and a very wide field of view. Principal Investigator: J. Huovelin, Observatory University of Helsinki, Finland.

Mercury Magnetospheric Orbiter (JAXA)
MMO will carry five advanced scientific experiments that will also be provided by nationally funded Principal investigators, one European and four from Japan. Significant European contributions are also provided to the Japanese instruments:

Mercury Magnetometer (MERMAG)
MERMAG will provide a detailed description of Mercury???s magnetosphere and of its interaction with the planetary magnetic field and the solar wind. Principal Investigator: W. Baumjohann, Austrian Academy of Sciences, Austria.

BepiColombo is Europe???s first mission to Mercury, the innermost planet of the Solar System. It consists of two orbiters, one for planetary investigation and one for magnetospheric studies. They will reach Mercury in 2019 after a six-year journey towards the inner Solar System to make the most extensive and detailed study of the planet ever performed.

The ‘Mercury Planetary Orbiter’ (MPO), under ESA???s responsibility, will study the surface and the internal composition of the planet at different wavelengths and with different techniques. The Mercury Magnetospheric Orbiter (MMO), under the responsibility of the Japan Aerospace Exploration Agency (ISAS/JAXA), will study the magnetosphere, that is the region of space around the planet that is dominated by its magnetic field.

Only two spacecraft have visited Mercury so far. NASA’s Mariner 10 provided the first close-up images of the planet when it flew past three times in 1974-75. More than 30 years later, on 14 January 2008, NASA???s MESSENGER swung-by Mercury, in the course of its journey to eventually settle in orbit around the planet in 2011.

The spacecraft provided new close-up images and scientific data of the planet. When it reaches its destination in 2019, BepiColombo will be only the second spacecraft to orbit Mercury in the history of planetary exploration.

The difficulty of reaching, surviving and operating in the harsh environment of a planet so close to Sun makes BepiColombo one of the most challenging long-term planetary projects undertaken by ESA so far.

BepiColombo was named after Giuseppe (Bepi) Colombo (1920-84), a scientist who studied Mercury’s orbital motion in detail and greatly contributed to the study of orbits and interplanetary travel.